US3127581A - Core and coil assembly - Google Patents

Description

March 31, 1964 w. A. RASMUSSEN CORE AND COIL ASSEMBLY Filed Oct. 28, 1959 gin Attorney.

United States Patent ice 3,127,581 CORE AND COIL ASSEMBLY Wayne A. Rasmussen, Rankin, Ill., assignor to General Electric Company, a corporation of New York Filed Oct. 28, 1959, Ser. No. 849,255 1 Claim. (Cl. 336-197) bled relation with the laminations of the magnetic core.

Where one or more coil assemblies are mounted on a laminated magnetic core member, which is a common practice in transformer and reactor construction, it is necessary that some means be provided to hold the coil assemblies in a fixed position on the magnetic core member and to maintain the laminations under the core assembly tightly in compression, so as to prevent vibration relative movement of the laminations, joint noise and air gaps between the laminations. It is desirable to provide such a means that will achieve these results as economically as possible.

In the past, wedges made out of wood, spring steel and other materials were interposed between the coil assembly and the laminated core member so as to exert a Wedging force that tends to urge the coil assembly against the laminations. Thus, in conventional coil and core constructions it is required that a separate wedge be inserted between the coil assembly and the core member and also that the inner portion of the coil assembly provide sufiicient clearance to allow the wedge to be inserted. In order to provide for this clearance, it is necessary to use a coil assembly having turns of greater mean effective length than would be required if the clearance did not have to be provided. Further, the wedge was an additional part that had to be manufactured and installed. Further, the conventional wedges made out of wood and other nonmagnetic materials are not a part of the magnetic circuit and are additional parts that must be manufactured for and installed in a core and coil assembly. Therefore, it is desirable that a means he provided for positioning coil assemblies in a tightly assembled relation with the laminations of the magnetic core that eliminates the aforementioned undesirable features.

It is, therefore, now the general object of this invention to provide an improved arrangement of a coil assembly and a laminated magnetic core section which will achieve the desired results as set forth above.

A more specific object of this invention is to provide an improved arrangement of a coil assembly and a magnetic core member which will permit coil assemblies of reduced means effective length to be used.

Another object of this invention is to provide a means for positioning a coil assembly in fixed relation to the magnetic core, that will also form a part of the magnetic circuit.

It is still a further object of this invention to provide an improved arrangement of a coil assembly and a magnetic core member that can be manufactured and assembled at reduced cost.

According to the invention, an arrangement of a coil assembly and a magnetic core member is provided whereby one or more lanced or raised portions are provided on at least one of the laminations of the magnetic core members and are disposed in a force exerting relationship with an inner portion of the coil assembly so as to position the coil assembly in a tightly assembled relation with the laminations of the magnetic core member.

In another aspect of the invention, a coil assembly is provided with an inner portion having an opening sufficient in cross sectional area to permit the coil assembly 3,127,581 Patented Mar. 31, 1964 to be passed over the plurality of thin superimposed laminations about which the coil is to be mounted but insufiicient in area to permit the coil assembly to readily pass over the one or more lanced or raised portions formed on the laminations. The coil assembly is thereupon forced over the lanced or raised portion and positioned in force exerting relationship with respect to the magnetic core member.

The subject matter which I regard as my invention is set forth in the appended claim. The invention itself, however, together with further objects and advantages thereof may be better understood by referring to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a view in perspective of two coil assemblies and the magnetic core structure of a ballast transformer illustrating a preferred embodiment of the invention;

FIG. 2 is a view in perspective of the magnetic core structure of the ballast transformer shown in FIG. 1, with one of the T-shaped laminations of the center leg displaced to illustrate the lanced or raised portion, the outline of the coil assemblies being shown in dashed lines;

FIG. 3 is, a sectional view along the line 33 of FIG. 1; and,

FIG. 4 is a view of the lanced or raised portions of the top laminations as seen along the line 4-4 of FIG. 2.

Referring now to FIGS. 1 and 2 of the drawings, there is shown a high reactance type of transformer 11 used for operating fluorescent lamps. The transformer 11 includes a magnetic core structure 12 made up of L-shaped sections 13 and 14 and a T-shaped center core section 15, the L-shaped sections being respectively located one on each side of the T-shaped center section as shown. Each section is made up of a plurality of superimposed laminations of relatively thin magnetic material. In the preferred embodiment, a pair of coil assemblies 16, 17 are provided which are positioned on the center magnetic core member. The details of the electrical connections have been omitted since they do not form a part of this invention.

All of the laminations lying in a given section are similar to all of the other laminations lying in the same stack with the exception of the lanced lamination 19 of the T-shaped core section 15, which has lanced or raised portions 20, 21, 22 in an engaging relationship with the inner portion 23 of the coil assemblies 16, 17. It will be noted that the central T-shaped section is provided with bridged portions 24, 25. 'Consequently, all of the laminations comprising this section must be properly aligned so that an uninterrupted bridged gap is formed. Due to the fact that the lamination 19 having the lanced portions 20, 21, 22 is of the same length, of the same general configuration and length as the other laminations in the stack, it can be seen that the lamination 19 can be readily positioned in alignment with the other laminations.

In accordance with the perferred practice of this invention, the lanced portions 20, 21, 22 are located along the center line of the laminations of the T-shaped section 15 so that the magnetic effect on the circuit is negligible. However, it should be readily apparent that in certain applications, it may be desirable to utilize in the magnetic circuit an opening which may be formed, if required, by the lancing operation. In such applications, all of the laminations in the stack would be lanced and each of the laminations in the stack would be interlocked and securely positioned against lateral displacement. Although only a single lamination having lanced portions is shown in the illustrated embodiment of the invention, it can be seen that more than one lanced lamination can be used. For example, a pair of lanced laminations can be advantageously used if the laminations are disposed at the opposite ends of the stack with the lanced portions extending outwardly to engage an inner portion of a coil assembly.

A further advantage of the arrangement of this invention is that annealed material can beused. Thus, the use of a lanced lamination of annealed material results in an increase of the effective stack height. In prior art constructions employing wedges of non-1nagnetic material or the spring action of a thin insert, the positioning means for coil assembly did not contribute to'the magnetic circuit. Accordingly, the invention presents a distinct advantage over such prior art construction of coil and core assemblies.

As shown in the sectional view of FIG. 3, the coil assembly 17 includes an outer protective wrapping 38, a coil winding 3%, and the inner portion or inner protective covering 23. The opening formed by the inner portion 23 is sufficient in size to permit the coil assembly 17 to pass over the level-surfaced laminations of section but is insufficient in size to readily pass over the lanced portions 20, 21 and 22. As the coil assembly 17 is forced over the lanced portions 2%, 21, the lanced portions 29, 21 impinge against the inner portion 23 and exert a force against the winding 39 resulting in a clamping action which tightly compresses the laminations.

Referring to FIG. 4, it will be seen that the lanced por tion is formed of extruded metal and has an elongated semi-ovoid configuration, which permits the coil assemblies 16, 17 to be inserted forcibly over section 15 without damaging the coil assemblies 16, 17. The lanced portion 20, as shown, is extruded without rupturing the lamination. As hereinbefore described, in some applications of this invention it may be desirable to form lanced portions with openings.

In order to hold the stacked laminations of sections 13, 14, 15 in an abutting relationship and to prevent them from vibrating when a 60 cycle current flows through the coil, there is provided a pair of identical retaining clamps 26, 27 on opposite sides of the transformer 11 as shown in FIG. 1. The retaining clamps 26, 27 are placed over the opposite ends of the T -shaped central section 15 and the two L-shaped sections 13, 14 hold the entire assembly together as well as tightly to compress the laminations.

Another advantage of the arrangement of the invention is that the respective laminations are of the same height and they can be readily clamped together into a tightly assembled relation by the clamps 26, 27. A flange 28 is formed with slots in the region where the butt joints between lamination stacks occur and define the flanged portions 29, 30, 31, 32 and 33. It is to be noted that the edges of the flanged central portion 31 lie in the same plane as the edges of outer flanged portions 29 39, 32, 33, which results in a more effective clamping arrangement than would be the case if the central flanged portion 31 had to be slightly raised to hold a wedge in compression as required in some constructions of the prior art.

The flange 28 of the clamp 26 is divided into the two pairs of flanged portions 29, 3t) and 32, 33, respectively, so when the identical clamp is used at either end, the slots will overlie the butt joints between the laminations of the L-shaped and T-shaped sections 13, 14. Obvious-' 1y, such an arrangement eliminates the need for fabricating an additional dissimilar part.

Sections 13 and 14, which are comprised of stacked L- shaped laminations, serve as the outer legs of the core assembly, and are held by the clamps 26, 27 in an abutting relationship with the T-shaped laminations of section 15 to form a closed magnetic circuit. It is to be noted that the recesses 34, 35 of the T-shaped laminations are the result of stamping the T-shaped laminations and the L-shaped laminations without waste of material from one sheet, the recesses 34, 35 providing the material for the projections 36, 37 of the L-shaped laminations. Thus, the window space may be augmented as required to accommodate coil assemblies of various sizes. 7

In accordance with this invention, the small raised portions 20, 21, 22 are lanced on the annealed T-shaped laminations used to form the central section. Since the lancing operation is performed on one of the same laminations used to make up the stack, it is not necessary to manufacture an additional part. It will be appreciated that the elimination of such a part in a mass production operation represents a considerable saving in manufacturing costs.

It will be noted that in accordance with the invention, the pressure exerted on the stack of laminations comprising the center core section 15 can be readily increased or decreased by increasing or decreasing the height ofthe raised portions 29, 21 and 22. In prior art constructions employing a bent member or a formed wedge, the pressure exerted on the laminations cannot be as easily adjust ed as in the present invention.

Another advantage of the arrangement of the core and coil assembly employing lanced lamination is that once the coil assemblies 16, 17 have been mounted on the stack of laminations that comprise the T-shaped section 15, the coil laminations are held in tightly assembled relation. During the manufacturing operation, the coil and core assemblies thus mounted can be easily handled and the subsequent manufacturing steps of assembling the outer lamination sections 13, 14 and installing the clamps 26, 27 can be readily accomplished. Thus, it can be seen that the arrangement of the present invention easily lends itself to a semiautomatic assembly method.

As shown in the dashed lines of FIG. 1, the lanced portions 21), 21, 22 engaging the coil assemblies 16, 17 are shown in a spaced relationship to each other. The lanced portion 22 engages the shorter coil assembly 16 and the lanced portions 20, 21 engage the longer coil assembly 17. It will, however, be understood that the lanced portions may be placed in any suitable location and that the lanced portions 219, 21, 22 were found, for the type of core and coil assembly used in the exemplification of this invention, to give satisfactory results. A principal function of the lanced portion is to engage the coil assemblies in a force exerting relationship and to be so spaced so that a sufficient number of pressure points will be provided along the inner portion of a coil assembly to hold the laminations in a tightly assembled relation.

It will be observed that according to the invention an easily manufactured lanced lamination is provided which performs the dual function of a wedging means and of a lamination. As hereinbefore described, the opening of the inner portion of a coil assembly need not include additional clearance such as would be required for a con? ventional wedge as used in the prior art to be provided be: tween the coil assembly and the laminations. Consequently, it is possible to utilize coil assemblies having turns of reduced mean length which results in a decreased amount of copper and paper required in the construction of coil assembly. Further, it is no longer necessary to use a separate wedging means in the construction of a core and coil assembly. Although in the illustrated embodiment of this invention, only one lamination having raised portions is shown. It is to be understood, however, that these raised portions may be lanced in more than one of the laminations for particular designs of a core and coil assembly.

While we have described above a particular embodi: ment of the invention, many modifications may be made. It is to be understood, therefore, that we intend by the appended claim to cover all such modifications that fall within the true spirit and scope of the invention.

I claim:

A magnetic core and coil assembly comprising a center core section on which at least one coil assembly is mounted, a pair of outer core sections forming a closed magnetic circuit with said center core section, a pair of in tightly assembled relation, said coil assembly having an inner portion dimensioned so as to provide only sufficient clearance to permit said coil assembly to be mounted on said center core section; and not less than one lanced portion on only the outermost one of said laminations of said center core section, said lanced portion projecting outwardly and in a force exerting relationship against said inner portion of said coil assembly so as to hold said laminations tightly in compression and to maintain said center core laminations and said coil assembly in tightly assembled relation, said lanced portion having an elongated semi-ovoid configuration extending longitudinally and centrally of said outermost lamination.

References Cited in the file of this patent UNITED STATES PATENTS

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